Beginning Android

 android:layout_height='fill_parent'
>
 <TextView android:id='@+id/dateAndTime'
  android:layout_width='fill_parent'
  android:layout_height='wrap_content'
 />
 <Button android:id='@+id/dateBtn'
  android:layout_width='fill_parent'
  android:layout_height='wrap_content'
  android:text='Set the Date'
 />
 <Button android:id='@+id/timeBtn'
  android:layout_width='fill_parent'
  android:layout_height='wrap_content'
  android:text='Set the Time'
 />
</LinearLayout>

The more interesting stuff comes in the Java source:

public class ChronoDemo extends Activity {
 DateFormat fmtDateAndTime = DateFormat.getDateTimeInstance ();
 TextView dateAndTimeLabel;
 Calendar dateAndTime = Calendar.getInstance();
 DatePickerDialog.OnDateSetListener d =
  new DatePickerDialog.OnDateSetListener() {
  public void onDateSet(DatePicker view, int year, int monthOfYear,
   int dayOfMonth) {
   dateAndTime.set(Calendar.YEAR, year);
   dateAndTime.set(Calendar.MONTH, monthOfYear);
   dateAndTime.set(Calendar.DAY_OF_MONTH, dayOfMonth);
   updateLabel();
  }
 };
 TimePickerDialog.OnTimeSetListener t =
  new TimePickerDialog.OnTimeSetListener() {
  public void onTimeSet(TimePicker view, int hourOfDay,
   int minute) {
   dateAndTime.set(Calendar.HOUR_OF_DAY, hourOfDay);
   dateAndTime.set(Calendar.MINUTE, minute);
   updateLabel();
  }
 };
 @Override
 public void onCreate(Bundle icicle) {
  super.onCreate(icicle);
  setContentView(R.layout.main);
  Button btn = (Button)findViewById(R.id.dateBtn);
  btn.setOnClickListener(new View.OnClickListener() {
   public void onClick(View v) {
    new DatePickerDialog(ChronoDemo.this, d,
     dateAndTime.get(Calendar.YEAR), dateAndTime.get (Calendar.MONTH),
     dateAndTime.get(Calendar.DAY_OF_MONTH)).show ();
   }
  });
  btn = (Button)findViewById(R.id.timeBtn);
  btn.setOnClickListener(new View.OnClickListener() {
   public void onClick(View v) {
    new TimePickerDialog(ChronoDemo.this, t,
     dateAndTime.get(Calendar.HOUR_OF_DAY), dateAndTime.get(Calendar.MINUTE),
     true).show();
   }
  });
  dateAndTimeLabel = (TextView)findViewById (R.id.dateAndTime);
  updateLabel();
 }
 private void updateLabel() {
  dateAndTimeLabel.setText(fmtDateAndTime.format (dateAndTime.getTime()));
 }
}

The “model” for this activity is just a Calendar instance, initially set to be the current date and time. We pour it into the view via a DateFormat formatter. In the updateLabel() method, we take the current Calendar, format it, and put it in the TextView.

Each button is given a OnClickListener callback object. When the button is clicked, either a DatePickerDialog or a TimePickerDialog is shown. In the case of the DatePickerDialog, we give it a OnDateSetListener callback that updates the Calendar with the new date (year, month, day of month). We also give the dialog the last-selected date, getting the values out of the Calendar. In the case of the TimePickerDialog, it gets a OnTimeSetListener callback to update the time portion of the Calendar,